From f0fe8227624d5c02715ed086867d12cd24f6ff47 Mon Sep 17 00:00:00 2001 From: Andrew Cooper Date: Thu, 27 Jun 2013 14:01:18 +0200 Subject: [PATCH] AMD/intremap: Prevent use of per-device vector maps until irq logic is fixed XSA-36 changed the default vector map mode from global to per-device. This is because a global vector map does not prevent one PCI device from impersonating another and launching a DoS on the system. However, the per-device vector map logic is broken for devices with multiple MSI-X vectors, which can either result in a failed ASSERT() or misprogramming of a guests interrupt remapping tables. The core problem is not trivial to fix. In an effort to get AMD systems back to a non-regressed state, introduce a new type of vector map called per-device-global. This uses per-device vector maps in the IOMMU, but uses a single used_vector map for the core IRQ logic. This patch is intended to be removed as soon as the per-device logic is fixed correctly. Signed-off-by: Andrew Cooper Acked-by: Suravee Suthikulpanit --- xen/drivers/passthrough/amd/pci_amd_iommu.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-) diff --git a/xen/drivers/passthrough/amd/pci_amd_iommu.c b/xen/drivers/passthrough/amd/pci_amd_iommu.c index 60696d74d8..5ea1a1d07d 100644 --- a/xen/drivers/passthrough/amd/pci_amd_iommu.c +++ b/xen/drivers/passthrough/amd/pci_amd_iommu.c @@ -223,8 +223,19 @@ int __init amd_iov_detect(void) { if ( amd_iommu_perdev_intremap ) { - printk("AMD-Vi: Enabling per-device vector maps\n"); - opt_irq_vector_map = OPT_IRQ_VECTOR_MAP_PERDEV; + /* Per-device vector map logic is broken for devices with multiple + * MSI-X interrupts (and would also be for multiple MSI, if Xen + * supported it). + * + * Until this is fixed, use global vector tables as far as the irq + * logic is concerned to avoid the buggy behaviour of per-device + * maps in map_domain_pirq(), and use per-device tables as far as + * intremap code is concerned to avoid the security issue. + */ + printk(XENLOG_WARNING "AMD-Vi: per-device vector map logic is broken. " + "Using per-device-global maps instead until a fix is found.\n"); + + opt_irq_vector_map = OPT_IRQ_VECTOR_MAP_GLOBAL; } else { @@ -235,6 +246,10 @@ int __init amd_iov_detect(void) else { printk("AMD-Vi: Not overriding irq_vector_map setting\n"); + + if ( opt_irq_vector_map != OPT_IRQ_VECTOR_MAP_GLOBAL ) + printk(XENLOG_WARNING "AMD-Vi: per-device vector map logic is broken. " + "Use irq_vector_map=global to work around.\n"); } if ( !amd_iommu_perdev_intremap ) printk(XENLOG_WARNING "AMD-Vi: Using global interrupt remap table is not recommended (see XSA-36)!\n"); -- 2.39.5